Heterogeneously integrated photonic circuit and method for manufacturing the circuit

ABSTRACT

The method for manufacturing the heterojunction circuit according to one embodiment of the present disclosure comprises depositing a first electrode on at least a part of a waveguide, moving a semiconductor comprising a second electrode at a lower end thereof onto the first electrode, and depositing a third electrode on an upper end of the semiconductor, wherein the waveguide and the semiconductor comprise different materials. Additionally, the moving step further comprises generating microbubbles by supplying heat to at least a part of the semiconductor, moving the semiconductor on the first electrode by moving the generated microbubbles, and removing the microbubbles by positioning the semiconductor on the first electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/366,534 filed on Mar. 27, 2019, which claims priority toKorean Patent Application No. 10-2018-0035740 filed on Mar. 28, 2018,which are incorporated herein in their entirety by reference for allpurposes.

TECHNICAL FIELD

The present disclosure relates to a heterogeneously integrated photoniccircuit and a method for manufacturing the same. More specifically, thepresent disclosure relates to a heterojunction circuit in which asemiconductor device and a photonic network including differentmaterials are bonded and a method for manufacturing the same.

BACKGROUND ART

With the advent of the information age, the importance of electronicdevices in the industry or daily life is gradually on the rise.Accordingly, the amount of information transmitted and received throughelectronic devices also increases. Electronic devices may use varioustechnologies for transmission and reception of information. For example,electronic devices may transmit and receive information throughcommunication using light, i.e., optical communication.

Optical communication may refer to a communication method in whichtransmission and reception of information is performed through opticalsignals. When using optical communication, electronic devices mayconvert an optical signal into an electrical signal, thereby finallyacquiring the information included in the optical signal. Meanwhile, foroptical communication, optical fibers for transmitting and receivingoptical signals are required. The optical fibers may include fibrouswaveguides for transmitting light. Waveguides on chips (semiconductorchips, or microchips) may be made of materials which allow high-speedcommunication, for example, silicon which is a material causing littleinterference. In this case, since silicon is an indirect band-gapmaterial, it may have low luminous efficiency which results inrestricting the efficiency of light sources or photodetectors.Accordingly, in order to improve the luminous efficiency, aheterojunction with a direct band-gap material may be required.Heterojunction may be performed by various methods. For example,heterojunction may be performed by partially growing a direct band-gapmaterial on an indirect band-gap material. Because of large mismatchesin lattice constants and thermal expansion coefficients between multiplesemiconductor materials, the heterojunction would require a lot of timeand high costs for large-area epitaxial growth.

SUMMARY

The present disclosure relates to a heterojunction circuit produced byefficiently bonding materials having different properties usingmicrobubbles and a method for manufacturing the same. Additionally, thepresent disclosure relates to a heterojunction circuit with minimizedwiring length by arranging a semiconductor which includes an electrodeat a lower end thereof on an electrode of a silicon waveguide, and amethod for manufacturing the same.

Meanwhile, the objectives of the present disclosure are not limited tothose mentioned above. Additionally, the present disclosure may includeobjectives which were not mentioned but could be clearly understood by aperson having an ordinary skill in the technical field to which thepresent disclosure belongs from the following descriptions.

In accordance with an aspect, there is provided a method formanufacturing a heterojunction circuit, comprising: depositing a firstelectrode on at least a part of a waveguide; moving a semiconductorcomprising a second electrode at a lower end thereof onto the firstelectrode; and depositing a third electrode on an upper end of thesemiconductor, wherein the waveguide and the semiconductor comprisedifferent materials.

The moving the semiconductor comprising: generating microbubbles bysupplying heat to at least a part of the semiconductor; moving thesemiconductor onto the first electrode by moving the generatedmicrobubbles; and removing the microbubbles by positioning thesemiconductor on the first electrode.

The generated microbubbles may be moved in response to movement of aheat source which applies heat to the semiconductor, and the removingthe microbubbles may comprise removing the microbubbles by stopping thesupply of heat.

The microbubbles may be generated at the upper end of the semiconductorto be bonded to the semiconductor.

The first electrode may comprise a first area and a second area, and thesemiconductor may be moved to be positioned on the first area, and themethod may further comprise: depositing a fourth electrode on the secondarea.

The first electrode may comprise a first area on which the semiconductoris positioned, and a second area and a third area distinguished from thefirst area, the first area and the second area may be connected by thethird area, and a fourth electrode may be deposited on an upper end ofthe second area.

The first electrode, the second electrode, the third electrode, and thefourth electrode may comprise the same material. Further, the firstelectrode and the second electrode may be connected, and the firstelectrode and the fourth electrode may be connected, so that the secondelectrode and the fourth electrode may be electrically connected.

The heterojunction circuit may further comprise an oxide film which ispositioned on an upper end of at least a part of the waveguide andseparated by a predetermined distance from the first electrode, and atleast a part of the third electrode and at least a part of the fourthelectrode may be positioned on an upper end of the oxide film.

A shape of the first area may correspond to a shape of the secondelectrode.

The waveguide may comprise silicon, and the semiconductor may comprise agroup III-V compound semiconductor.

In accordance with another aspect, there is provided a heterojunctioncircuit, comprising: a waveguide comprising silicon; a first electrodedeposited on at least a partial area of the waveguide; a semiconductorwhich comprises a second electrode at a lower end thereof and ispositioned so that the second electrode is adjacent to the firstelectrode; and a third electrode deposited on an upper end of thesemiconductor, wherein the semiconductor and the silicon comprisedifferent materials.

The first electrode may comprise a first area on which the semiconductoris positioned, and a second area and a third area distinguished from thefirst area, the first area and the second area may be connected by thethird area, and a fourth electrode may be deposited on an upper end ofthe second area.

The first electrode, the second electrode, the third electrode, and thefourth electrode may comprise the same material. Further, the firstelectrode and the second electrode may be connected, and the firstelectrode and the fourth electrode may be connected, so that the secondelectrode and the fourth electrode may be electrically connected.

The heterojunction circuit may further comprise an oxide film which ispositioned on an upper end of at least a part of the waveguide andseparated by a predetermined distance from the first electrode, and atleast a part of the third electrode and at least a part of the fourthelectrode may be positioned on an upper end of the oxide film.

A shape of the first area may correspond to a shape of the secondelectrode.

The semiconductor may comprise a group III-V compound semiconductor.

The heterojunction circuit according to one embodiment of the presentdisclosure and a method for manufacturing the same may provide aheterojunction circuit with minimized wiring length by bonding asemiconductor device and a silicon waveguide including differentmaterials using microbubbles.

The effects which could be obtained in the present disclosure are notlimited to those mentioned above, and other effects which are notmentioned could be clearly understood by a person skilled in the artfrom the following descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of the configuration of a heterojunctioncircuit according to one embodiment of the present disclosure;

FIG. 2 illustrates an example of a method for manufacturing aheterojunction circuit according to one embodiment of the presentdisclosure;

FIGS. 3A to 3C illustrate an example of the configuration of the circuitaccording to each step in the method for manufacturing theheterojunction circuit according to one embodiment of the presentdisclosure;

FIG. 4 illustrates an example of a method for manufacturing theheterojunction circuit using microbubbles according to one embodiment ofthe present disclosure;

FIGS. 5A to 5C illustrate an example of the constitution of theheterojunction circuit according to each step in the method formanufacturing the heterojunction circuit using microbubbles according toone embodiment of the present disclosure;

FIGS. 6A to 6C illustrate an example of generating microbubblesaccording to one embodiment of the present disclosure;

FIGS. 7A and 7B illustrate an example for explaining the heterojunctioncircuit manufactured according to one embodiment of the presentdisclosure;

FIGS. 8A and 8B illustrate an example for explaining the effect of theheterojunction circuit manufactured according to one embodiment of thepresent disclosure; and

FIGS. 9A to 9C illustrate another example for explaining the effect ofthe heterojunction circuit according to one embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The advantages and features of the present disclosure and the methods ofaccomplishing these will be clearly understood from the followingdescription taken in conjunction with the accompanying drawings.However, embodiments are not limited to those embodiments described, asembodiments may be implemented in various forms. It should be noted thatthe present embodiments are provided to make a full disclosure and alsoto allow those skilled in the art to know the full range of theembodiments. Therefore, the embodiments are to be defined only by thescope of the appended claims.

In describing the embodiments of the present disclosure, if it isdetermined that detailed description of related known components orfunctions unnecessarily obscures the gist of the present disclosure, thedetailed description thereof will be omitted. Further, the terminologiesto be described below are defined in consideration of functions of theembodiments of the present disclosure and may vary depending on a user'sor an operator's intention or practice. Accordingly, the definitionthereof may be made on a basis of the content throughout thespecification.

FIG. 1 illustrates an example of the configuration of a heterojunctioncircuit according to one embodiment of the present disclosure. FIG. 1illustrates an example of a cross-section of the heterojunction circuit100. Meanwhile, the heterojunction circuit 100 in FIG. 1 is merely oneembodiment of the present disclosure, and thus the present disclosure isnot limited to FIG. 1.

When referring to FIG. 1, the heterojunction circuit 100 may comprisesupporters in a semiconductor substrate, a semiconductor (asemiconductor device, a micro-disk, or a light source/a photodetector)105, and/or electrodes 101, 102, 103.

The supporters in the semiconductor substrate may comprise a silicon(Si) substrate (or a wafer) 107 on which an oxide film 109 is formed.The oxide film 109 may be formed of silicon dioxide (hereinafter,“SiO₂”), and the silicon substrate 107 may be formed of silicon. Thesupporters in the semiconductor substrate may comprise silicon (orsilicon film) 111 and/or an oxide film 113 on an upper end of the oxidefilm 109. The silicon 111 may be generated by depositing silicon on anupper end of the oxide film 109, and etching the deposited silicon inthe same shape as the silicon 111 in FIG. 1. The oxide film 113 may begenerated by depositing SiO₂ on an upper end of the silicon 111. Thethickness of SiO₂ (e.g., 2 μm) deposited on an upper end of the silicon111 may vary depending on the embodiments. The oxide film 113 may begenerated by etching SiO₂ deposited on an upper end of the silicon 111.

Silicon 111 has low interference, and thus may enable high-speedtransmission of optical signals. Accordingly, silicon 111 may be used asa material of a waveguide for high-speed optical communication. Inoptical communication, the waveguide may serve as a passage fortransmitting and receiving optical signals.

Hereinafter, in the present disclosure, the waveguide may refer to apart in the supporters in the semiconductor substrate having a carved(or groove) shape. Meanwhile, in the embodiment, since the silicon 111is an indirect band-gap material, when electrons and holes are coupled,an energy corresponding to the band-gap of the silicon 111 may beconsumed as heat or vibration.

The oxide film 113 may be separated by a predetermined distance from thefirst electrode 101 and may be positioned on an upper end of at least apart of the waveguide.

The supporters in the semiconductor substrate may include basic elementsof a semiconductor circuit for implementing silicon photonicstechnologies. Meanwhile, the supporters in the semiconductor substrateare not limited to the above-mentioned examples.

The semiconductor 105 may include a compound semiconductor (or a groupIII-V compound semiconductor). For example, the semiconductor 105 may bea semiconductor formed of at least one of indium (In), gallium (Ga) andarsenic (As). As another example, the semiconductor 105 may be acompound semiconductor formed of InGaAs. This semiconductor 105 may be adirect band-gap semiconductor. When electrons and holes are coupled, thedirect band-gap semiconductor may include a semiconductor which emitsenergy in the form of light. The energy may include an energycorresponding to the band-gap of the semiconductor 105.

The electrodes may include a first electrode 101, a second electrode102, and a third electrode 103. The first electrode 101 may include anelectrode wired in at least a part of an upper end of the waveguide. Thesecond electrode 102 may include an electrode positioned on (or attachedto) a lower end of the semiconductor 105. According to the embodiments,as illustrated in FIG. 1, the width of the second electrode 102 issmaller than that of the semiconductor 105, and may correspond to thatof the first electrode 101. Meanwhile, the width of the second electrode102 is not limited to the above-mentioned examples, but may have varioussizes as long as the second electrode 102 could be positioned on top ofthe first electrode 101 or on the lower end of the semiconductor 105.The third electrode 103 may be generated based on a metallizationprocess.

The thicknesses of the first electrode 101, the second electrode 102,and the third electrode 103 may be different. For example, the thicknessof the first electrode 101 may be 200 nm, the thickness of the secondelectrode 102 may be 100 nm, and the thickness of the third electrode103 may be 1.5 μm.

The first electrode 101, the second electrode 102, and the thirdelectrode 103 may have different thicknesses depending on the materialsincluded therein. For example, when the first electrode 101 includestitanium (Ti), the thickness of the first electrode 101 may be 20 nm,and when the first electrode 101 includes gold (Au), the thickness ofthe first electrode 101 may be 200 nm. As another example, when thesecond electrode 102 includes titanium, the thickness of the secondelectrode 102 may be 7 nm, and when the second electrode 102 includesgold, the thickness of the second electrode 102 may be 100 nm. As yetanother example, when the third electrode 103 includes titanium, thethickness of the third electrode 103 may be 10 nm, and when the thirdelectrode 103 includes gold, the thickness of the third electrode 103may be 1.5 μm. The materials constituting the first electrode 101, thesecond electrode 102, and the third electrode 103 are not limited to theabove-mentioned examples, but may include various materials which couldbe used as the electrode.

The heterojunction circuit 100 may include an indirect band-gap material(e.g., silicon 111) and a direct band-gap material (e.g., semiconductor105). Specifically, the heterojunction circuit 100 may have a structurein which an indirect band-gap material and a direct band-gap materialare bonded. For example, the heterojunction circuit 100 may include thesilicon 111 and the semiconductor 105 which are bonded (or coupled) toeach other. According to the embodiments, the indirect band-gap materialand direct band-gap material may be bonded to each other havingelectrodes positioned therebetween. For example, the semiconductor 105and the silicon 111 may be bonded to each other having the firstelectrode 101 and the second electrode 102 positioned therebetween. Theheterojunction circuit 100 including the silicon 111 and a semiconductor105 which are bonded to each other may supplement the properties of thesilicon 111 as an indirect band-gap material. For example, theheterojunction circuit 100 may supplement the low luminous efficiency ofthe silicon 111 by using the semiconductor 105 with high luminousefficiency.

The heterojunction circuit 100 may include electrodes on an upper endand a lower end of the semiconductor 105. Specifically, theheterojunction circuit 100 may include a third electrode 103 on theupper end of the semiconductor 105, and may include the second electrode102 and the first electrode 101 on the lower end of the semiconductor105. The first electrode 101 may be bonded to the second electrode 102to operate as one electrode. Due to the electrodes directly connected tothe upper end and the lower end of the semiconductor 105, theheterojunction circuit 100 does not need an additional wiring. In otherwords, the heterojunction circuit 100 of the present disclosure mayinclude minimized electrode wiring. Due to the electrode wiring withminimized length, the heterojunction circuit 100 may have a fastresponse speed in relation to detecting optical signals.

Although it is not illustrated, the first electrode 101 positioned onthe lower end of the semiconductor 105 may be wired linearly along thelength of the waveguide on at least a part of the silicon 111constituting the waveguide. The semiconductor 105 may be positioned onat least a part of the first electrode 101. The first electrode 101 mayinclude a part (or an area) on which the semiconductor 105 is positionedor a part on which the semiconductor 105 is not positioned. The part ofthe first electrode 101 on which the semiconductor 105 is not positionedmay be connected to another electrode. By such a connection, the firstelectrode 101 may be extended to be positioned on the same plane as thethird electrode 103. The first electrode 101 and the other electrode ofthe part on which the semiconductor 105 is not positioned may be bondedto each other to operate as one electrode. Explanation in relation withthis configuration will be described later with reference to FIGS. 3A to3C.

FIG. 2 illustrates the steps in the method for manufacturing theheterojunction circuit 100 in which the semiconductor and waveguidecomprising different materials are bonded to each other according to oneembodiment of the present disclosure. The operation which will bementioned later may be performed by a semiconductor device or anelectronic device, and since this operation may be easily achieved by aperson skilled in the art, detailed description thereon will be omitted.

Referring to FIG. 2, the method for manufacturing the heterojunctioncircuit 100 may comprise a step of depositing a first electrode 101 onat least a part of a waveguide (S210). In some embodiments, the firstelectrode 101 may be deposited (or wired, or generated) linearly alongthe length of the waveguide. In other embodiments, the first electrode101 may be generated by depositing the electrode on silicon 111, andthen etching the deposited electrode to have a linear shape extending inthe longitudinal direction of the waveguide.

The method for manufacturing the heterojunction circuit 100 may comprisea step of moving a semiconductor 105 comprising a second electrode 102at a lower end thereof onto the first electrode 101 of the waveguide(S220). A semiconductor 311 including the second electrode 102 at alower end thereof may be moved to a designated area of the firstelectrode 101. The second electrode 102 at a lower end of thesemiconductor 105 may be attached on the designated area of the firstelectrode 101. The attachment between the second electrode 102 and thefirst electrode 101 may be made by the attraction formed by Van derWaals force.

The method for manufacturing the heterojunction circuit 100 may comprisea step of depositing a third electrode 103 on an upper end of thesemiconductor 105 (S230). The third electrode 103 may be deposited onthe upper end of the semiconductor 105 positioned on a designated areaof the waveguide. Although it is not illustrated, the step (S230) maycomprise a step of depositing the third electrode 103 on an upper end ofanother designated area of the first electrode.

FIG. 3 illustrates an example of the configuration of the circuitaccording to each step in the method for manufacturing theheterojunction circuit according to one embodiment of the presentdisclosure.

Referring to FIG. 3, a first electrode 309 (e.g., the first electrode101 in FIG. 1) may be wired on a silicon 307 (e.g., silicon 111 inFIG. 1) of the waveguide. The first electrode 309 may be wired linearlyin the longitudinal direction of the waveguide. The first electrode 309may comprise a first area 302 having a similar shape to the shape of asemiconductor 311 (e.g., the semiconductor 105 in FIG. 1). For example,the first electrode 309 may comprise a circular first area 302 which hasthe same shape as the circular semiconductor 311. According to theembodiments, the first electrode 309 may comprise a second area 304which is separated from the first area 302. The first area 302 and thesecond area 304 may be connected by a third area 306. The third area 306may comprise a part of the first electrode 309 wired in a linear shapebetween the first area 302 and the second area 304. The first area 302,the second area 304, and the third area 306 may have various shapes, andthe shapes thereof are not limited to the illustrated examples.

The semiconductor 311 may comprise a second electrode 313 (e.g., thesecond electrode 102) at a lower end thereof. The second electrode 313may be attached or bonded to the lower end of the semiconductor 311. Thesecond electrode 313 may be an electrode generated by an additionalprocess. For example, the second electrode 313 may be an electrode whichis generated by an additional apparatus for generating the secondelectrode, and is then attached to the semiconductor 311. The secondelectrode may be generated by an additional process before orsimultaneously with the step of manufacturing the heterojunction circuit100.

The second electrode 313 may have various shapes. For example, thesecond electrode 313 may have a shape (e.g., circular shape)corresponding to the semiconductor 311. As another example, the secondelectrode 313 may have a different shape (e.g., square shape) which issmaller than the semiconductor 311. As yet another example, the secondelectrode 313 may have a shape which is smaller than the semiconductor311 and corresponds to the shape of the semiconductor 105. Meanwhile,the shapes of the second electrode 313 are not limited to theabove-mentioned examples, but the second electrode 313 may have variousshapes as long as it could be bonded (or easily bonded) to the firstarea 302.

The semiconductor 311 may be moved onto the first area 302 of the firstelectrode 309. As the semiconductor 311 moves onto the first area 302, acircuit hetero-bonded with a part of the waveguide (e.g., silicon 307)may be formed. Explanation on the movement of the semiconductor 311 onthe first electrode 309 will be described later with reference to FIGS.4 to 6.

A third electrode 315 may be deposited on an upper end of thesemiconductor 311. A part of the third electrode 315 may be positionedon the upper end of the semiconductor 311, and another part of the thirdelectrode 315 may be positioned on an upper end of an oxide film 319. Insome cases, a fourth electrode 317 may be deposited on an upper end ofthe second area 304 of the first electrode 309. A part of the fourthelectrode 317 may be positioned on the upper end of the second area 304of the first electrode 309, and another part of the fourth electrode 317may be positioned on the upper end of the oxide film 319. In this case,the fourth electrode 317 may be positioned on the same plane as thethird electrode 315. The fourth electrode 317 may be a part which isextended in order to use the first electrode 309 bonded to the lower endof the semiconductor 311. The fourth electrode 317, for example, may bean extension of the first electrode 309 for providing a specific signal(e.g., an optical signal or an electrical signal) to the first electrode309 or for detecting the same. The fourth electrode 317 is connected tothe first electrode 309 to operate as one electrode with the firstelectrode 309. In other words, the first electrode 309 and the fourthelectrode 317 may be driven as one electrode during the operation of theheterojunction circuit 100.

As the electrode is connected to the upper end and the lower end of thesemiconductor 311, the wiring length of the heterojunction circuit 100may be minimized. As the wiring length is minimized, the moving distancebetween the electrons and/or holes of the heterojunction circuit 100 maybe minimized. Accordingly, the time constant (or RC time constant),and/or the transition time of the heterojunction circuit 100 may beimproved. Additionally, as the wiring length is minimized, theheterojunction circuit 100 may have a high level of responsivity (or afast response speed) or a low level of dark current. When theheterojunction circuit 100 has a low level of dark current, aphotodetector using the heterojunction circuit 100 may detect smalloptical signals while maintaining linearity.

FIG. 4 illustrates an example of the method for manufacturing theheterojunction circuit using microbubbles according to one embodiment ofthe present disclosure. FIG. 4 illustrates an example of the method formoving the semiconductor 311 onto the first electrode 309 usingmicrobubbles. The operation which will be mentioned later may beconducted by a semiconductor device or an electronic device, and anyexplanation overlapping with FIG. 2 or 3 will be omitted.

According to one embodiment, the operation for generating microbubblesor the operation using microbubbles may be conducted in water. Forexample, the following operations could be conducted while the circuitfor heterojunction and the semiconductor (e.g., semiconductor 311) forheterojunction are put in water.

Referring to FIG. 4, the method for manufacturing the heterojunctioncircuit 100 may comprise a step of providing heat to the semiconductor311 to generate microbubbles (S410). The method for manufacturing theheterojunction circuit 100 may supply heat to at least a part of thesemiconductor 311 by using a heat supply device as a heat source. Theheat supply device may include, for example, a laser. When heat issupplied to the semiconductor 311, microbubbles may be generated at anupper end of the semiconductor 311. FIGS. 5A to 5C or FIGS. 6A to 6C maybe referred to as examples in relation with the generation ofmicrobubbles.

The method for manufacturing the heterojunction circuit 100 may comprisea step of moving the semiconductor 311 onto the first electrode 309 ofthe waveguide (S420). Microbubbles may be moved by the movement of thesupplied heat. As the microbubbles move, the microbubbles and thesemiconductor 311 attached thereto may be moved together. In otherwords, as heat is moved on the first electrode 309, the microbubbles andthe semiconductor 311 attached to the microbubbles could be moved ontothe first electrode 309. The semiconductor 311 positioned on the firstelectrode 309 may be connected (or bonded) to the first electrode 309 asthe second electrode 313 attached to the lower end of the semiconductor311 is in contact with the first electrode 309. For example, the secondelectrode 313 may be put on the upper end of the first electrode 309 tobe connected to the first electrode 309. The second electrode 313 mayoperate as the first electrode 309 by being connected to the firstelectrode 309. In other words, the first electrode 309 and the secondelectrode 313 may be driven as one electrode during the operation of theheterojunction circuit 100.

The method for manufacturing the heterojunction circuit 100 may comprisea step of removing the microbubbles (S430). As the semiconductor 311 ispositioned on the upper end of the first electrode 309, the microbubblescan be removed. The microbubbles can be removed by stopping the supplyof heat to the semiconductor 311. FIGS. 5A to 5C may be referred to asan explanation on the removal of microbubbles.

FIGS. 5A to 5C illustrate an example of the configuration of theheterojunction circuit according to each step in the method formanufacturing the heterojunction circuit using microbubbles according toone embodiment of the present disclosure.

Referring to FIGS. 5A to 5C, microbubbles 520 may be generated as heat510 is supplied to the top of the semiconductor 311. While microbubbles520 are generated on the top of the semiconductor 311, the microbubbles520 may be coupled to the semiconductor 311. In this case, thesemiconductor 311 may comprise the second electrode 313 at a lower endthereof. The second electrode 313 may be generated and attached to thesemiconductor 311 in advance. FIGS. 6A to 6C may be referred to asdetailed description on the generation of microbubbles 520.

When the semiconductor 311 is positioned on the first electrode 309, thesupply of heat 510 may be stopped. As the supply of heat 510 is stopped,the size of the microbubbles 520 is reduced gradually. The microbubblesmay extinguish as a predetermined time passes after the supply of heatis stopped. As the supply of heat 510 is stopped and the microbubbles520 are removed, only the semiconductor 311 may be positioned on thefirst electrode 209.

FIGS. 6A to 6C illustrate an example of generating the microbubblesaccording to one embodiment of the present disclosure.

When referring to FIG. 6, heat 510 may be supplied to a part of theupper end of the semiconductor 311. In accordance with the supply ofheat, the microbubbles 520 are generated, and a convectional flow (e.g.,thermos-capillary phenomenon) may occur around the boundary between thesemiconductor 311 and water. Due to the convectional flow generated, thesemiconductor 311 may be coupled (or attached) to the microbubbles 520.Heat 510 may be supplied continuously, and in this case, thesemiconductor 311 may be moved to a place where the temperature is highaccording to the movement of heat 510.

The semiconductor 311 may be formed of InGaAsP (or a compoundsemiconductor). In this case, the semiconductor 311 may efficientlyconvert the supplied heat into thermal energy. Accordingly, even ifthere is no absorption layer (or a metal layer, or a dielectric layer)for converting optical energy of the heat source into thermal energy,the microbubbles 520 may be generated as heat is supplied. Since thereis no absorption layer, the heterojunction circuit 100 does not have toput up with optical loss which may be caused by the absorption layer inthe step of implementing the photonic circuit after heterojunction.

FIGS. 7A and 7B illustrate an example for explaining the heterojunctioncircuit manufactured according to one embodiment of the presentdisclosure.

Referring to FIG. 7A, in one embodiment, a circuit 701 represents aheterojunction circuit in which a semiconductor (e.g., the semiconductor105 in FIG. 1) is bonded to a single-mode waveguide. The graph 702represents the grating coupler output power of the circuit 701 accordingto wavelength. The grating coupler output power may include the strengthof the optical signal output by using a grating coupler. The graph 702shows that a whispering gallery mode excited by optical pumping could bedelivered well through the single-mode waveguide. The whispering gallerymode may include the light which stays in a circular optical resonatorfor a long time.

Referring to FIG. 7B, in one embodiment, a circuit 703 represents aheterojunction circuit in which the semiconductor is hetero-bonded witha multi-mode waveguide. The graph 704 represents the grating coupleroutput power of the circuit 703 according to wavelength. The graph 704shows that a whispering gallery lasing mode excited by optical pumpingcould be delivered well through the multi-mode waveguide.

FIGS. 8A and 8B illustrate an example for explaining the effect of theheterojunction circuit manufactured according to one embodiment.

Referring to FIGS. 8A and 8B, in one embodiment, the graph 801 mayrepresent a maximum output power of an optical signal before and afterusing microbubbles (e.g., microbubbles 520 of FIGS. 5A to 5C) accordingto an effective pump power of the optical signal provided to theheterojunction circuit. The effective pump power may be a termindicating an optical signal which is substantially injected in theheterojunction circuit among the optical signals provided in theexperiment. The maximum output power of the optical signal may be a termindicating a maximum value among the output power of the optical signaloutput through the waveguide after optical signals flow in theheterojunction circuit.

The maximum output power of the optical signal before using microbubblesmay be the maximum output power of the optical signal output beforeadjusting the semiconductor (e.g., semiconductor 105 of FIG. 1) usingthe microbubbles, that is, the maximum output power of the opticalsignal output when providing the optical signal on SiO₂. The maximumoutput power of the optical signal after using microbubbles may be themaximum output power of the optical signal output after adjusting thesemiconductor using the microbubbles, that is, the maximum output powerof the optical signal when providing the optical signal to thesemiconductor coupled to the waveguide. The graph 801 shows that thephysical damage may not occur in the semiconductor and/or waveguide inthe process of moving the semiconductor by the microbubbles. Themicrobubbles move the semiconductor using an indirect force generated bythe heat, thereby preventing damages (or scratches) to the semiconductorand/or waveguide.

The table 803 in FIG. 8B represents an alignment error according to thetype and/or size of the semiconductor according to one embodiment of thepresent disclosure. Referring to table 803, the semiconductor may havevarious sizes. The semiconductor may, for example, include asemiconductor having a predetermined diameter of 5 μm or more and 16 μmor less. The semiconductors having different sizes may have amisalignment. The misalignment may be, for example, 213 nm or 284 nm.Meanwhile, it may be known that the misalignment exists within apredetermined size of error (e.g., 500 nm or less). In other words, itmay be known that the heterojunction circuit according to one embodimentof the present disclosure is manufactured with low misalignment and withhigh accuracy.

FIGS. 9A to 9C illustrate another example for explaining the effect ofthe heterojunction circuit according to one embodiment. FIGS. 9A to 9Cillustrate the result of an experiment performed to confirm the propertyof the heterojunction circuit according to one embodiment of the presentdisclosure.

Referring to the graph 901 in FIG. 9A, it may be known that theheterojunction circuit has a very low dark current of about 2 nA up to abackward voltage of −1 V.

When referring to the graph 903 in FIG. 9B, it may be known that theheterojunction circuit may detect a small optical signal, for example,an optical signal of 1 μW while maintaining linearity.

The graph 905 in FIG. 9C represents a result of measuring radiofrequency (RF) response. According to the graph 905, it may be knownthat the 3 dB bandwidth of the heterojunction circuit is 52 GHz, whichis a very fast response speed. Additionally, although it is notillustrated, the heterojunction circuit may obtain a clear eye diagramfor a 50 Gb/s non-return-to-zero (NRZ) signal. Through the above, it maybe known that the heterojunction circuit may deliver the optical signalclearly.

According to FIGS. 9A to 9C, the heterojunction circuit has an improvedRC time constant and/or transition time by minimizing the movingdistance of the electrons and holes compared to a mesa electrodestructure which was conventionally used.

As described above, those skilled in the art will understand that thepresent disclosure can be implemented in other forms without changingthe technical idea or essential features thereof. Therefore, it shouldbe understood that the above-described embodiments are merely examples,and are not intended to limit the present disclosure. The scope of thepresent disclosure is defined by the accompanying claims rather than thedetailed description, and the meaning and scope of the claims and allchanges and modifications derived from the equivalents thereof should beinterpreted as being included in the scope of the present disclosure.

What is claimed is:
 1. A heterojunction circuit, comprising: a waveguidecomprising silicon; a first electrode deposited on at least a partialarea of the waveguide; a second electrode adjacent to the firstelectrode; a semiconductor to which the second electrode attached at alower end thereof; and a third electrode deposited on an upper end ofthe semiconductor, wherein the semiconductor and the silicon comprisedifferent materials.
 2. The heterojunction circuit of claim 1, whereinthe first electrode comprises a first area on which the semiconductor ispositioned, and a second area and a third area distinguished from thefirst area, the first area and the second area are connected by thethird area, and a fourth electrode is deposited on an upper end of thesecond area.
 3. The heterojunction circuit of claim 2, wherein the firstelectrode, the second electrode, the third electrode, and the fourthelectrode comprise the same material, and the first electrode and thesecond electrode are connected, and the first electrode and the fourthelectrode are connected, so that the second electrode and the fourthelectrode are electrically connected.
 4. The heterojunction circuit ofclaim 2, wherein the heterojunction circuit further comprises an oxidefilm which is positioned on an upper end of at least a part of thewaveguide and separated by a predetermined distance from the firstelectrode, and at least a part of the third electrode and at least apart of the fourth electrode are positioned on an upper end of the oxidefilm.
 5. The heterojunction circuit of claim 2, wherein a shape of thefirst area corresponds to a shape of the second electrode.
 6. Theheterojunction circuit of claim 2, wherein the semiconductor comprises agroup III-V compound semiconductor.
 7. The heterojunction circuit ofclaim 1, wherein the first electrode and the second electrode aredeposited between the semiconductor and the waveguide.